1. Field of the Invention
This invention relates to a tractor having a vehicle frame with a p air of right and left elongate frame members spaced from each other and extending in a longitudinal direction and interconnected in intermediate positions by a cross member, an engine supported by the elongate frame members in a front region of the vehicle frame, a rear axle unit connected to rear axle connecting members fixed to the elongate frame members in a rear region of the vehicle frame, and a drive transmitting mechanism for transmitting drive from the engine to the rear axle unit, a front loader and/or a backhoe being attachable to a front and a rear of the tractor as supported by the vehicle frame.
2. Description of the Related Art
A tractor with a front loader and a backhoe attachable thereto as noted above, i.e. a so-called tractor-front loader-backhoe (TLB), is subjected to overloads such as compressive, tensile, twisting and bending forces acting on a vehicle frame when running with the backhoe attached to the rear end or during an excavating operation with the backhoe. Thus, the tractor must have a highly strong chassis to withstand such heavy loads. TLBs with such strong chassis are known from U.S. Pat. Nos. 4,087,009 and 4,661,036, for example.
Further, it is common practice to connect a reinforcing frame unit to a rear region of a vehicle frame to which a backhoe is attached, whereby the entire vehicle frame becomes strong enough to withstand overloads occurring when running with the backhoe attached to the rear end or during an excavating operation with the backhoe. Tractors with such reinforcing frames are known from U.S. Pat. Nos. 5,000,269 and 5,248,237, for example. U.S. Pat. No. 6,056,502 discloses a technique of connecting a front end of a reinforcing frame to a forward region of a vehicle frame by a flexible structure.
In any case, in connecting a reinforcing frame unit to a rear region of a vehicle frame, according to conventional practice, reinforcing frame connections are formed on the vehicle frame adjacent connections of a rear axle unit fixed to the vehicle frame.
That is, in the prior art noted above, a structure elastically deformable relatively freely is not provided between the rear axle connections and the reinforcing frame connections that are formed adjacent each other on the vehicle frame. Consequently, overloads occurring when running with a backhoe attached to the rear end or during an excavating operation with the backhoe are transmitted straight to the axle unit. It is therefore necessary for the casing of the rear axle unit also to have sufficient strength to withstand such overloads. As a result, the rear axle unit tends to be large and expensive to manufacture. It is difficult to attach a backhoe to a small tractor, in particular, for which lightweight and low cost are desired features.
The object of this invention is to suppress transmission to a rear axle unit of overloads occurring when running with a backhoe attached to the rear end or during an excavating operation with the backhoe, thereby to avoid an enlargement and increased manufacturing cost of the rear axle unit due to reinforcement, for example, of the casing of the rear axle unit.
The above object is fulfilled, according to this invention, by a tractor having a vehicle frame with a pair of right and left elongate frame members spaced from each other and extending in a longitudinal direction and interconnected in intermediate positions by a cross member, an engine supported by the elongate frame members in a front region of the vehicle frame, a rear axle unit connected to rear axle connecting members fixed to the elongate frame members in a rear region of the vehicle frame, and a drive transmitting mechanism for transmitting drive from the engine to the rear axle unit, a front loader and/or a backhoe being attachable to a front and a rear of the tractor as supported by the vehicle frame, the tractor comprising a reinforcing frame unit for reinforcing the vehicle frame, and reinforcing frame connecting members for connecting the reinforcing frame unit to the vehicle frame, wherein the reinforcing frame connecting members are spaced horizontally and/or vertically from the rear axle connecting members.
With this construction, the reinforcing frame unit connected to the vehicle frame gives the latter increased strength for withstanding overloads such as compressive, tensile, twisting and bending forces occurring when the tractor runs with the backhoe attached or during an excavating operation with the backhoe. Further, the vehicle frame has the reinforcing frame connecting members and rear axle connecting members spaced from each other as noted above. The frame portions in between act as flexible structure portions relatively freely and elastically deformable when the tractor runs with the backhoe attached or during an excavating operation with the backhoe. The elastic deformation of these frame portions absorbs overloads occurring when the tractor runs or during an excavating operation, thereby suppressing transmission of the overloads to the rear axle unit. This invention effectively avoids an enlargement and increased manufacturing cost of the rear axle unit due to reinforcements of a casing and the like of the rear axle unit, and allows attachment of a backhoe to a small tractor for which lightweight and low cost are desired.
In a preferred embodiment of this invention, the reinforcing frame unit is in form of a gate-shaped frame including a pair of right and left side members and a horizontal member interconnecting upper positions of the side members, and the reinforcing frame connecting members are formed in lower end regions of the side members and rear end regions of the elongate frame members, the side members further forming backhoe attaching members. With this construction, the rear end region of the vehicle frame has increased strength, and the backhoe may be attached to the rear end region having the increased strength, without a special, additional frame member for defining the backhoe attaching portions. A frame portion, between the rear axle connecting member and the reinforcing frame connecting member to which the reinforcing frame connecting member of one of the side members is connected, of each of the right and left frame members acts as a flexible structure portion relatively freely and elastically deformable. The elastic deformation of this frame portion absorbs the overloads occurring when the tractor runs with the backhoe attached or during an excavating operation with the backhoe, thereby suppressing transmission of the overloads to the rear axle unit
Another preferred embodiment of this invention provides brace members each connected at one end thereof to one of the side members, and at the other end to a position of one of the elongate frame members vertically spaced from one of the rear axle connecting members. With this construction, the gate-shaped frame to which the backhoe is attached has increased supporting strength. Loads acting on the gate-shaped frame are distributed to the right and left elongate frame members and the right and left brace members. Further, a frame portion of each of the right and left elongate frame members between a connection to the brace member and the rear axle connecting member, as well as the frame portion of each elongate frame member between the rear axle connecting member and the reinforcing frame connecting member, acts as a flexible structure portion relatively freely and elastically deformable. The elastic deformation of the frame portions of the right and left elongate frame members between the rear axle connecting members and the reinforcing frame connecting members absorbs components distributed to the right and left elongate frame members of the overloads occurring when the tractor runs with the backhoe attached or during an excavating operation with the backhoe, thereby suppressing transmission of the overload components to the rear axle unit. The elastic deformation of the frame portions of the right and left elongate frame members between the connections to the brace members and the rear axle connecting members absorbs load components distributed to the right and left brace members, thereby suppressing transmission of the overload components to the rear axle unit.
In a further preferred embodiment of this invention, the reinforcing frame unit is in form of at least one cross frame interconnecting rear end regions of the elongate frame members. With this construction, the rear end region of the vehicle frame is reinforced by the cross frame interconnecting rear end regions of the right and left elongate frame members. Further, a rearward frame portion between the rear axle connecting member and a connection to the cross member of each of the right and left elongate frame members acts as a flexible structure portion relatively freely and elastically deformable. The elastic deformation of these frame portions absorbs the overloads occurring when the tractor runs with the backhoe attached or during an excavating operation with the backhoe, thereby suppressing transmission of the overloads to the rear axle unit.
In a further preferred embodiment of this invention, the reinforcing frame unit includes elongate reinforcing frames extending along outer faces of the elongate frame members, respectively, and one of the reinforcing frame connecting members is formed in a rear end region of each of the reinforcing frames and a rear end region of each of the elongate frame members, and the other of the reinforcing frame connecting members is formed in a forward end region of each of the reinforcing frames and a forward end region beyond an engine mounting portion of each of the elongate frame members. With this construction, the overloads occurring when the tractor runs with the backhoe attached or during an excavating operation with the backhoe are distributed to the right and left elongate frame members and right and left reinforcing frames. A frame portion between the rear axle connecting member and the reinforcing frame connecting member in the rear end region of each of the right and left elongate frame members, and a frame portion of each of the right and left reinforcing frames between the rear reinforcing frame connecting member connected to the reinforcing frame connecting member of the elongate frame member and the front reinforcing frame connecting member connected to the reinforcing frame connecting member of the elongate frame member, act as flexible structure portions relatively freely and elastically deformable. The elastic deformation of the frame portions between the rear axle connecting members and the reinforcing frame connecting members in the rear end regions of the right and left elongate frame members absorbs components distributed to the right and left elongate frame members of the overloads occurring when the tractor runs with the backhoe attached or during an excavating operation with the backhoe, thereby suppressing transmission of the overload components to the rear axle unit. The elastic deformation of the frame portions between the front and rear reinforcing frame connecting members of the right and left reinforcing frames absorbs load components distributed to the right and left reinforcing frames, thereby avoiding transmission thereof to the rear axle unit.
In a further preferred embodiment of this invention, the reinforcing frame unit includes elongate reinforcing frames extending along outer faces of the elongate frame members, respectively, the elongate frame members have front loader post support members projecting laterally outwardly of longitudinally intermediate portions thereof, and one of the reinforcing frame connecting members is formed in a rear end region of each of the reinforcing frames and a rear end region of each of the elongate frame members, and the other of the reinforcing frame connecting members is formed in a forward end region of each of the reinforcing frames and each of the front loader post support members. With this construction, the overloads occurring when the tractor runs with the backhoe attached or during an excavating operation with the backhoe are distributed to the right and left elongate frame members and right and left reinforcing frames. A frame portion between the rear axle connecting member and the reinforcing frame connecting member in the rear end region of each of the right and left elongate frame members, and a frame portion of each of the right and left reinforcing frames between the rear reinforcing frame connecting member connected to the rear reinforcing frame connecting member of one of the elongate frame member and the front reinforcing frame connecting member connected to one of the front loader post support members, act as flexible structure portions relatively freely and elastically deformable. The elastic deformation of the frame portions between the rear axle connecting members and the reinforcing frame connecting members in the rear end regions of the right and left elongate frame members absorbs components distributed to the right and left elongate frame members of the overloads occurring when the tractor runs with the backhoe attached or during an excavating operation with the backhoe, thereby suppressing transmission of the overload components to the rear axle unit. The elastic deformation of the frame portions between the front and rear reinforcing frame connecting members of the right and left reinforcing frames absorbs load components distributed to the right and left reinforcing frames and transmits the load components to the front loader post support members, thereby avoiding transmission thereof to the rear axle unit.
In a further preferred embodiment of this invention, the reinforcing frame unit includes reinforcing frames extending along outer faces of the elongate frame members, respectively, the reinforcing frame connecting members are formed in a rear end region of each of the reinforcing frames and a rear end region of each of the elongate frame members, and the reinforcing frames are connected to the rear axle unit in positions spaced from the rear axle connecting members. With this construction, the overloads occurring when the tractor runs with the backhoe attached or during an excavating operation with the backhoe are distributed to the right and left elongate frame members 4 and right and left reinforcing frames. A frame portion between the rear axle connecting member and the reinforcing frame connecting member of each of the right and left elongate frame members, and a frame portion between a connection to one of the rear axle cases and the rear reinforcing frame connecting member of each of the right and left reinforcing frames, act as flexible structure portions relatively freely and elastically deformable. The elastic deformation of the frame portions between the rear axle connecting members and the reinforcing frame connecting members of the right and left elongate frame members absorbs components distributed to the right and left elongate frame members of the overloads occurring when the tractor runs with the backhoe attached or during an excavating operation with the backhoe, thereby suppressing transmission of the overload components to the rear axle unit. The elastic deformation of the frame portions between the connections to the rear axle cases and the rear reinforcing frame connecting portions in the rear end regions of the right and left reinforcing frames, absorbs load components distributed to the right and left reinforcing frames, thereby suppressing transmission thereof to the rear axle unit.
Other features and advantages of this invention will be apparent from the following description of the embodiments to be taken with reference to the drawings.